Very Large Scale Integration

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Very-large-scale integration (VLSI) is the process of creating an

Before the introduction of VLSI technology, most ICs had a limited set of functions they could perform. An electronic circuit might consist of a CPU, ROM, RAM and other glue logic. VLSI enables IC designers to add all of these into one chip.

History

Background

The

With the small transistor at their hands, electrical engineers of the 1950s saw the possibilities of constructing far more advanced circuits. However, as the complexity of circuits grew, problems arose.^[1] One problem was the size of the circuit. A complex circuit like a computer was dependent on speed. If the components were large, the wires interconnecting them must be long. The electric signals took time to go through the circuit, thus slowing the computer.^[1]

The invention of the integrated circuit by Jack Kilby and Robert Noyce solved this problem by making all the components and the chip out of the same block (monolith) of semiconductor material. The circuits could be made smaller, and the manufacturing process could be automated. This led to the idea of integrating all components on a single-crystal silicon wafer, which led to small-scale integration (SSI) in the early 1960s, and then medium-scale integration (MSI) in the late 1960s.

VLSI

The first semiconductor chips held two transistors each. Subsequent advances added more transistors, and as a consequence, more individual functions or systems were integrated over time. The first integrated circuits held only a few devices, perhaps as many as ten diodes, transistors, resistors and capacitors, making it possible to fabricate one or more logic gates on a single device. Now known retrospectively as small-scale integration (SSI), improvements in technique led to devices with hundreds of logic gates, known as medium-scale integration (MSI). Further improvements led to large-scale integration (LSI), i.e. systems with at least a thousand logic gates. Current technology has moved far past this mark and today's microprocessors have many millions of gates and billions of individual transistors.

At one time, there was an effort to name and calibrate various levels of large-scale integration above VLSI. Terms like ultra-large-scale integration (ULSI) were used. But the huge number of gates and transistors available on common devices has rendered such fine distinctions moot. Terms suggesting greater than VLSI levels of integration are no longer in widespread use.

In 2008, billion-transistor processors became commercially available. This became more commonplace as semiconductor fabrication advanced from the then-current generation of

Structured VLSI design is a modular methodology originated by Carver Mead and Lynn Conway for saving microchip area by minimizing the interconnect fabric area. This is obtained by repetitive arrangement of rectangular macro blocks which can be interconnected using wiring by abutment. An example is partitioning the layout of an adder into a row of equal bit slices cells. In complex designs this structuring may be achieved by hierarchical nesting.^[4]

Structured VLSI design had been popular in the early 1980s, but lost its popularity later^[

approach by procedure nesting to avoid chaotic spaghetti-structured programs.

Difficulties

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As microprocessors become more complex due to technology scaling, microprocessor designers have encountered several challenges which force them to think beyond the design plane, and look ahead to post-silicon:

• Process variation – As photolithography techniques get closer to the fundamental laws of optics, achieving high accuracy in doping concentrations and etched wires is becoming more difficult and prone to errors due to variation. Designers now must simulate across multiple fabrication process corners before a chip is certified ready for production, or use system-level techniques for dealing with effects of variation.
• Stricter design rules – Due to lithography and etch issues with scaling, design rule checking for layout has become increasingly stringent. Designers must keep in mind an ever increasing list of rules when laying out custom circuits. The overhead for custom design is now reaching a tipping point, with many design houses opting to switch to electronic design automation (EDA) tools to automate their design process.
• multiprocessor architectures, since an overall speedup
  can be obtained even with lower clock frequency by using the computational power of all the cores.
• First-pass success – As
  DFT), and Design for X
  .
• Electromigration

See also

• Application-specific integrated circuit
• Caltech Cosmic Cube
• Interface logic model
• List of semiconductor fabrication plants
• Mead–Conway VLSI chip design revolution
• Neuromorphic engineering
• Polycrystalline silicon
• System on a chip (SoC)

References

1. ^ ^{a b} "The History of the Integrated Circuit". Nobelprize.org. Archived from the original on 29 Jun 2018. Retrieved 21 Apr 2012.
2. ^ "1964: First Commercial MOS IC Introduced". Computer History Museum.
3. JSTOR 24923169
   .
4. ISBN 9788182202153
   . Retrieved 2 May 2017.

Further reading

• Baker, R. Jacob (2010). CMOS: Circuit Design, Layout, and Simulation, Third Edition. Wiley-IEEE. pp. 1174.
  ISBN 978-0-470-88132-3. http://CMOSedu.com/
• Weste, Neil H. E. & Harris, David M. (2010). CMOS VLSI Design: A Circuits and Systems Perspective, Fourth Edition. Boston: Pearson/Addison-Wesley. p. 840.
  ISBN 978-0-321-54774-3. http://CMOSVLSI.com/
• Chen, Wai-Kai (2007). The VLSI handbook. Boca Raton, FL: CRC/Taylor & Francis.
  OCLC 83977431
  .
• ISBN 0-201-04358-0.{{cite book}}: CS1 maint: multiple names: authors list (link
  )

External links

• Lectures on Design and Implementation of VLSI Systems at Brown University
• Design of VLSI Systems